The goal of the proposed research is to determine the function of the adipocyte fatty acid binding protein (AFABP) in the transport and metabolism of fatty acids in adipose tissue. Fatty acid trafficking is central to the ability of adipose tissue to store and mobilize energy, and imbalances in the control of fatty acid metabolism accompany obesity, insulin resistance, and diabetes. AFABP is believed, but have never been directly proven, to be centrally important in the transport of fatty acids. This study utilizes transgenic mice in which the AFABP gene has been disrupted by homologous recombination and which lack the AFABP protein. Given the abundance and tissue-specificity of AFABP, the absence of the protein should alter adipocyte lipid homeostasis. Using the AFABP-knockout mice, the proposed research will investigate the role of AFABP in fatty acid transport into and within adipocytes, as well as in the regulation of white and brown adipocyte lipid metabolism.